#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	int a, b, c, d,max;
	int max4(int a, int b, int c, int d);
	printf("please enters 4 interger numbers:");
	scanf("%d%d%d%d", &a, &b, &c, &d);
	max = max4(a, b, c, d);
	printf("max = %d", max);
	return 0;
}

int max4(int a, int b, int c, int d)
{
	int max2(int a, int b);
	int m;
	m = max2(a, b);
	m = max2(m, c);
	m = max2(m, d);
	return m;
}

int max2(int a, int b)
{
	if (a > b)
	{
		return a;
	}
	else
		return b;
}